Development and Internal Validation of a Multivariable Prognostic Model for in-Hospital Mortality in Critically Ill Patients with Acute Exacerbation of COPD.

Purpose: Acute exacerbations of chronic obstructive pulmonary disease (COPD) requiring intensive care unit (ICU) admission are associated with substantial mortality. Although the Acute Physiology and Chronic Health Evaluation II (APACHE II) score is widely used for prognostic assessment, its complexity and limited disease-specific applicability have prompted the development of simpler prognostic models. Therefore, this study aimed to develop and internally validate a multivariable prognostic model for predicting in-hospital mortality in critically ill patients with acute exacerbation of COPD and to compare its performance with APACHE II. Patients and Methods: This retrospective observational study included 392 adult patients admitted to the ICU with acute exacerbation of COPD between January 2022 and December 2025. Demographic characteristics, laboratory findings, arterial blood gas parameters, Charlson Comorbidity Index, and APACHE II scores were recorded. Independent predictors of mortality were identified using multivariable logistic regression. Model discriminatory performance was assessed using receiver operating characteristic (ROC) curve analysis, while calibration was evaluated using the Hosmer-Lemeshow test and calibration plots. Internal validation was performed using 1000 bootstrap resamples. Results: A total of 392 patients were included, of whom 94 (23.9%) died during hospitalization. Multivariable logistic regression identified age, male sex, urea, albumin, C-reactive protein (CRP), and Charlson Comorbidity Index as independent predictors of in-hospital mortality. The final prediction model demonstrated excellent discriminatory performance (AUC 0.899, 95% CI 0.865-0.927) and significantly outperformed APACHE II (AUC 0.813, 95% CI 0.771-0.851; DeLong p = 0.0014). Calibration was good according to the Hosmer-Lemeshow test (p = 0.066), and internal validation using 1,000 bootstrap resamples confirmed model stability. Conclusion: A multivariable prognostic model based on six routinely available admission variables demonstrated excellent discriminatory performance and good calibration for predicting in-hospital mortality in critically ill patients with acute exacerbation of COPD. The model showed higher discriminatory performance than APACHE II in our cohort. Nevertheless, external validation and direct comparison with established COPD-specific prognostic models are required before routine clinical implementation.